G. Ghirlanda
A5036418646- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Particle Detector Development and Performance
- Radio Astronomy Observations and Technology
- Dark Matter and Cosmic Phenomena
- Nuclear Physics and Applications
- Galaxies: Formation, Evolution, Phenomena
- Cosmology and Gravitation Theories
- Astronomical Observations and Instrumentation
- Statistical and numerical algorithms
- Neutrino Physics Research
- Advanced X-ray and CT Imaging
- Particle Accelerators and Free-Electron Lasers
- SAS software applications and methods
- Planetary Science and Exploration
- Medical Imaging Techniques and Applications
- CCD and CMOS Imaging Sensors
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
- COVID-19 diagnosis using AI
Brera Astronomical Observatory
2015-2024
Istituto Nazionale di Fisica Nucleare, Sezione di Milano Bicocca
2018-2024
National Institute for Astrophysics
2012-2024
Astronomical Observatory of Rome
2021-2023
Istituto di Astrofisica Spaziale e Fisica cosmica di Palermo
2023
Centre National de la Recherche Scientifique
2021-2023
University of Milano-Bicocca
2017-2022
University of Leicester
2022
Fondazione Bruno Kessler
2022
Institut de Recherche sur les Lois Fondamentales de l'Univers
2019-2021
We consider all bursts with known redshift and $νF_ν$ peak energy, $E^{obs}_{peak}$. For a good fraction of them an estimate the jet opening angle is available from achromatic break their afterglow light curve. This allows derivation collimation--corrected energy bursts, $E_γ$. The distribution values $E_γ$ more spread respect to previous findings, covering about two orders magnitude. find surprisingly tight correlation between source frame $E_{peak}$: $E^{obs}_{peak}(1+z) \propto...
We studied all blazars of known redshift detected by the Fermi satellite during its first 3-month survey. For majority them, pointed Swift observations ensure a good multiwavelength coverage, enabling us to reliably construct their spectral energy distributions (SEDs). model SEDs using one-zone leptonic and study derived interesting physical parameters as function observed γ-ray luminosity. confirm previous findings concerning relation with source luminosity which are at origin blazar...
We report our observation of the short gamma-ray burst (GRB) GRB 170817A, associated to binary neutron star merger gravitational wave (GW) event GW 170817, performed in X-ray band with XMM-Newton 135 d after (on 29 December, 2017). find evidence for a flattening light curve respect previously observed brightening. This is also supported by nearly simultaneous optical Hubble Space Telescope and successive Chandra low-frequency radio observations recently reported literature. Since...
The binary neutron star merger event GW170817 was detected through both electromagnetic radiation and gravitational waves. Its afterglow emission may have been produced by either a narrow relativistic jet or an isotropic outflow. High-spatial-resolution measurements of the source size displacement can discriminate between these scenarios. We present very-long-baseline interferometry observations, performed 207.4 days after using global network 32 radio telescopes. apparent is constrained to...
Abstract The Einstein Probe (EP) is an interdisciplinary mission of time-domain and X-ray astronomy. Equipped with a wide-field lobster-eye focusing imager, EP will discover cosmic transients monitor the variability known sources in 0.5–4 keV, at combination detecting sensitivity cadence that not accessible to previous current monitoring missions. can perform quick characterisation or outbursts Wolter-I telescope onboard. In this paper, science objectives are presented. expected enlarge...
Optical and near-infrared observations of the gamma-ray burst GRB 031203, at z = 0.1055, are reported. A very faint afterglow is detected superposed onto host galaxy in our first infrared JHK observations, carried out ~9 hr after burst. Subsequently, a rebrightening all bands, peaking R band about 18 rest-frame days The closely resembles light curve supernova like SN 1998bw, assuming that went off almost simultaneously, but with somewhat slower evolution. Spectra taken close to maximum show...
We study the emission observed at energies greater than 100 MeV of 11 Gamma Ray Bursts (GRBs) detected by Fermi/Large Area Telescope (LAT) until October 2009. The GeV has three main properties: (i) its duration is often longer softer Burst Monitor (GBM) onboard Fermi [this confirms earlier results from Energetic Gamma-Ray Experiment (EGRET)]; (ii) spectrum consistent with F(v) propto v^(-1) and does not show strong spectral evolution; (iii) for brightest bursts, flux LAT decays as a power...
We study the BL Lac objects detected in one year all sky survey of Fermi satellite, with a energy spectral slope alpha_gamma [0.1-100 GeV] band greater than 1.2. In vs gamma-ray luminosity plane, these Lacs occupy region populated by Flat Spectrum Radio Quasars (FSRQs). Studying properties their distributions (SED) and emitting lines, we find that several have SED similar to FSRQs they do broad lines large equivalent width, should be reclassified as even adopting current phenomenological...
Abstract TeV photons from blazars at relatively large distances, interacting with the optical–infrared cosmic background, are efficiently converted into electron–positron pairs. The produced pairs extremely relativistic (Lorentz factors of order 106– 107) and promptly lose their energy through inverse Compton scatterings microwave producing emission in GeV band. spectrum flux level this reprocessed critically dependent on intensity intergalactic magnetic field, B, that can deflect diluting...
We consider the 1.5 years Fermi Large Area Telescope light curves (E > 100 MeV) of flat spectrum radio quasars 3C 454.3 and PKS 1510-089, which show high activity in this period time. characterise duty cycle source by comparing time spent sources at different flux levels. detail covering periods extreme flux. The large number high-energy photons collected LAT these events allows us to find evidence variability on timescales few hours. discuss implications significant such short timescales,...
We present a carefully selected sub-sample of Swift long gamma-ray bursts (GRBs) that is complete in redshift. The sample constructed by considering only with favorable observing conditions for ground-based follow-up searches, which are bright the 15–150 keV Swift/BAT band, i.e., 1-s peak photon fluxes excess to 2.6 photons s−1 cm−2. composed 58 bursts, 52 them redshift completeness level 90%, while another two have constraint, reaching 95%. For three we no constraint on high allows us first...
We present the results of spectral analysis public data 438 gamma ray bursts (GRBs) detected by Fermi Gamma Burst Monitor (GBM) up to March 2010. For 432 we could fit time-integrated spectrum. In 318 cases reliably constrain peak energy their νFν spectrum analyzing between 8 keV and 35 MeV. Eighty percent these spectra are fitted a power-law with an exponential cutoff, remaining Band function. Among GRBs, 274 belong long GRB class 44 short. Long GRBs have typical ~ 160 low-energy index α −...
We compare the spectral properties of 79 short and long Gamma-Ray Bursts (GRBs) detected by BATSE selected with same limiting peak flux. Short GRBs have a low-energy component harder energy slightly higher than GRBs, but no difference is found when comparing GRB spectra those first 1-2 s emission GRBs. These results confirm earlier findings for brighter The bolometric flux correlates their in similar way to bursts. populate different regions fluence-peak plane, bursts being less energetic...
We reconsider the emission properties of BL Lac objects emitting in high-energy gamma-ray band exploiting new information MeV-GeV obtained by Large Area Telescope (LAT) onboard Fermi Gamma-Ray Space its first three months operation. To this aim we construct spectral energy distribution all Lacs revealed LAT and known TeV not detected LAT, also including data from Swift satellite, model them with a simple one-zone leptonic model. The analysis shows that (being or already band) share similar...
We use a nearly complete sample of gamma-ray bursts (GRBs) detected by the Swift satellite to study correlations between spectral peak energy Epeak prompt emission, isotropic energetics Eiso and luminosity Liso. This GRB is characterized high level completeness in redshift (90 per cent). allows us probe an unbiased way issue related physical origin these against selection effects. find that one burst, 061021, outlier Epeak–Eiso correlation. Despite this case, we strong Epeak–Liso for sample....
We estimate the bulk Lorentz factor Gamma_0 of 31 GRBs using measured peak time their afterglow light curves. consider two possible scenarios for Gamma_0: case a homogeneous circumburst medium or wind density profile. The values are broadly distributed between few tens and several hundreds with average ~138 ~66 profile, respectively. find that isotropic energy luminosity correlate in similar way Gamma_0, i.e. Eiso Gamma_0^2 Liso Gamma_0^2, while Epeak Gamma_0. These correlations less...
Long-duration Gamma-Ray Bursts (GRBs) are an extremely rare outcome of the collapse massive stars, and typically found in distant Universe. Because its intrinsic luminosity ($L\sim 3 \times 10^{53}$ erg s$^{-1}$) relative proximity ($z=0.34$), GRB 130427A was a unique event that reached highest fluence observed gamma-ray band. Here we present comprehensive multiwavelength view with Swift, 2-m Liverpool Faulkes telescopes by other ground-based facilities, highlighting evolution burst emission...
We present a carefully selected sample of short gamma-ray bursts (SGRBs) observed by the Swift satellite up to June 2013. Inspired criteria we used build similar bright long GRBs (the BAT6 sample), SGRBs with favorable observing conditions for redshift determination on ground, ending 36 events, almost half which measure. The completeness increases about 70% (with an average value z = 0.85) restricting those events that are in 15-150 keV Burst Alert Telescope energy band. Such flux-limited...
We derive the luminosity function φ(L) and redshift distribution Ψ(z) of short gamma-ray bursts (SGRBs) using all available observer-frame constraints (i.e. peak flux, fluence, energy duration distributions) large population Fermi SGRBs rest-frame properties a complete sample detected by Swift. show that steep ∝ L− α with ≥ 2.0 is excluded if full set considered. implement Markov chain Monte Carlo method to functions assuming intrinsic Ep−Liso Ep−Eiso correlations hold or, alternatively,...
Knowledge of the bulk Lorentz factor $\Gamma_{0}$ GRBs allows us to compute their comoving frame properties shedding light on physics. Upon collisions with circumburst matter, fireball a GRB starts decelerate, producing peak or break (depending density profile) in curve afterglow. Considering all bursts known redshift and an early coverage emission, we find 67 optical GeV curves at time $t_{\rm p}$. For another 106 set upper limit p}^{\rm UL}$. We show that p}$ is due dynamics deceleration...
In this paper, we compute rest-frame extinctions for the afterglows of a sample Swift gamma-ray bursts (GRBs) complete in redshift. The selection criteria are based on observational high-energy parameters prompt emission and therefore our should not be biased against dusty sight-lines. It is expected that inferences hold general population GRBs. Our main result optical/near-infrared extinction GRB does follow single distribution. 87 per cent events absorbed by less than 2 mag, 50 suffer from...